The Allegro library provides C/C++ programmers low level routines
commonly needed in game programming, such as input, graphics, midi,
sound effects, and timing. It is cross platform and works with many
different compilers.  Originally developed by Shawn Hargreaves, it is
now a group project with contributions from all over the world! Some
of its key features include:

    * Ease of Use - comes with comprehensive documentation and examples
    * Extensibility - if the built-in functionality isn't enough, there
      are many add-ons available
    * Cross Platform - without changing a single line of code, you can
      create versions for Windows, OS X, Linux, DOS, and others! Works
      with many compilers, including DJGPP and VC++
    * Open Source - anyone can contribute, including you!
    * Free - it won't cost you a dime, and there are no restrictions on
      its usage
